Different units of time:Below are some of the words used to define units of time:Chronon is one-billionth of a trillionth of a second (the time of a photon would take to cross the width of 1 electron at the speed of light).femtosecond is 0.000000000000001 of a secondPicosecond is measured as one-trillionth of a secondNanosecond is one-millionth of a secondA millisecond is one- thousandth (0.001) of a second: the blink of an takes 50-80 millisecondscentisecond is one-hundredth (0.01) of a secondSecond is 1/60 of a minute1 minute = 60 seconds1 hour = 60 minutesDay- Sunrise to sunset, or midnight to midnight or sunset to sunset= 24 hoursWeek = seven days, also known as seven nights or sennight in Shakespearean timesFortnight = two weeks (from the old English for 14 nights)Month- full Moon to full Moon, 1/12 of a year, four weeks or 28,29,30 or 31 days depending on the monthbimester - two monthstrimester- a period of 3 monthsyear - 365 days, 12 months or 52 weeksSolar day - The time it takes for a place on the Earth directly facing the Sun to make one revolution and return to the same position (approx. 23 hours 56 minutes)Solar year- The time taken for the Earth to make a complete revolution around the Sun equal to 362.24219 solar days or 365 days 5 hours 48 minutes 45.51 seconds, also called a astronomical or tropical year.Leap year= 366 daysdecade= 10 years, also known as decenniumcentury= 100 yearsmillennium= 1,000 years also called as chiliadbimillennium= 2,000 yearsEra is a period of time measured from some important eventeon or aeon is a long period of time, usually thousands of years, it is one-billion year in geology and astronomyepoch is a very long period of time or a geological era.

Leap seconds:The rotation of the Earth is slowing down which means that a solar day (the time it takes the Earth to make one complete revolution) and the time shown by atomic clocks would constantly diverge. This problem has been solved by adding leap seconds. Since 1072, there have been 22 leap seconds. The last one was added on 31 December 2005, which delayed New Year's day 2006 by one second.Naming the days of the week:The days of the week are called after planets and other objects saw in the sky by the Ancient Babylonians, the the Romans.Monday is the Moon's dayTuesday is Tiu's day, Mars or the Roman god of war adopted as the great warrior Tiw or Tiu in Scandinavian mythology.Wednesday is Woden's dayThursday is Thor's day, Thor was the god of ThunderFriday is Freyja's day like Venus. Frigg or Freyja was the goddess of love.Saturday is Saturn's daySunday is the Sun's dayCalendar:The Gregorian Calendar is used by most of the world's countries and culture, but some base their calendars on more ancient systems. An alternative calendar has adopted by other countries at some point in their history.

3761 BC

Jewish calendar starts

2637 BC

Original Chinese calendar starts

45 BC

Roman Empire adopted Julian Calendar

0

Christian Calendar starts

79

Hindu Calendar starts

597

In Britain Julian calendar adopted

622

Islamic calendar starts

1582

Gregorian calendar introduced in Catholic countries

1752

Julian calendar abandoned, Gregorian calendaradopted in Britain and its colonies, including America